Lubricating grease



Patented Nov. 25, 1952 LUBRIOATING GREASE George F. Ford, Bartlesville,kla., assignor to Phillips Petroleum Company, a corporation of DelawareNo Drawing. Application January 4, 1950, Serial No. 136,839

' 3 Claims.

This invention relates to greases. In one aspect, this invention relatesto a grease having properties normally attributed to gel greases andproperties normally attributed to fiber greases. In another aspect, itrelates to a greasehaving properties superior to many properties ofgreases normally called gel greases and of greases normally called fibergreases.

In the art of grease-making, both gel greases and fiber greases areknown. In some cases, the same ingredients may be used to make these twogreases and the type of grease produced is governed by the processthrough which the grease is manufactured. Lubricating greases mostcommonly are comprised of a lubricating oil and an alkali metal salt ofa fatty acid, although fatty acid salts other than alkali metal saltsmay frequently be used.

Fiber greases are usually produced by a process in which initially a fator tallow is saponified by caustic alkali in the presence of a portionof the lubricating oil, this saponification being carried out at atemperature approximately at the boiling point of the caustic solutionafter which the temperature is raised to 220-240 F. so that at leastmost of the water present is vaporized and removed from thegrease-making vessel. The mass present in the kettle is agitated orstirred during the process to facilitate saponification and to aid inthe formation of a fibrous structure in the oil-soap mixture. Additionaloil is added during the dehydration and cooling stages to bring thecomposition to the proper proportion of oil and soap. The temperaturerange during the oil addition may range from 240 F. down to about 140 F.or even lower. It will be noted that in this procedure, the grease willcontain, in addition to oil and soap, some glycerol and unvaporizedwater, which are ordinarily not objectionable. In some cases, however,fatty acids are neutralized in the presence of the oil instead ofsaponification of glycerides in which case greases containingsubstantially no glycerine are formed. Numerous modifications of theseprocesses may be used, relatively slow cooling of these greases beingdesirable in at least most cases.

In the production of a gel grease, a neutral soap, such as a metal saltof a fatty acid, is heated with oil to a temperature sufficiently abovethe melting point of the soap that with slight stirring a single liquidphase is produced. This liquid is then cooled, preferably quickly, andthe grease produced has a gel structure. The grease may subsequently'beWorked to produce a smooth grease of desirable characteristics.

Gel greases are most suitably produced from high viscosity index, lowviscosity oils and metal salts of fatty acids. Viscosity index(hereinafter called V. I.) is a measure of the change in viscositycaused by change in temperature, an oil having a high viscosity indexchanging less in viscosity over a given temperature range than onehaving a lower index, see Dean 8; Davis, Chem. Sz Met. Eng. 36, 618(1929). The oils are suitably from 100 to 700 viscosity SayboltUniversal seconds (hereinafter called S. U. S.) preferably from 150 to500 S. U. S., at 100 F., and with a V. I. of or above. Suitable soapsinclude those not only containing an alkali metal radical, but alsoaluminum, barium, etc. Gel-type greases, especially those containingalkali metal soaps, have the ability to lubricate high speed bearings,have excellent work stability, good operational temperature range, andbetter oxidation stability. However, they do not cling to metalsurfaces, are not good sealants, bleed excessively on standing, tend tospatter, and will not return to their original condition if overheated.v

The fiber greases are most suitably produced from low V. I. (e. g. lessthan 90), high Viscosity (e. g. greater than 150 S. U. S. and preferablygreater than 500 S. U. S. at F.) oils and an alkali metal salt of afatty acid, usually the sodium salt. These fiber greases are good inmany applications because of their ability to adhere to metal surfaces.Also, these greases are readily sealed in bearings with simple,economical seals, thus not having to be replaced often due to leakage orpresence of foreign material, such as dust and dirt, which hasworkedinto the bearing. However, the fiber greases are not satisfactory forlubrication of high speed bearings, are useful only over a relativelysmall range of temperatures, and have poor work stability, completelylosing their body, or resistance to penetration by a conical object, inabout onehundredth the number of milling or working strokes that a gelgrease can easily stand without any substantial loss of body. By themilling or working strokes is meant the number of strokes on a greaseworker carried out according to standard procedure with an AN-G worker(Army-Navy grease worker).

The numerical values of the penetration as given herein aremioropenetrator values. Micropenetrator values are penetration valuesmade according to the A. S. T. M. Test D-21'7- l4'1, but modified so asto use a micropenetrator needle, plunger, and cup, as described byKaufman, Finn and Harrington in Industrial and Engineering Chemistry,Analytical Edition 11, 108-110 (1939).

Gel greases having satisfactory lubricating properties can seldom bemade with oils having viscosities higher than 500 to 700 S. U. S.However, gel type greases made from oils of higher viscosities aredesirable and are often needed. My invention, therefore, permits theincorporation of such a higher viscosity oil (in the form of a fibergrease) in a gel type grease. The resulting grease then contains atleast a substantial proportion of high viscosity oil and at the sametime passes properties of a gel type grease.

Blending of a high viscosity oil directly with a gel grease usuallyproduces a fiuid mass without grease structure and is, therefore, not asatisfactory grease. When mixing a high viscosity oil with a melted soapaccording to usual procedure for making a gel grease, and after cooling,the mass is thick and of little lubricating value.

An object of my invention is to provide a grease having propertiesnormally attributed to those of gel greases and properties normallyattributed to fiber greases.

Another object of my invention is to provide a grease having someproperties superior to those normally attributed to gel and to fibergreases.

Another object of my invention is to provide amethod for the productionof a grease having properties superior to some of the properties of gelgreases and fiber greases.

Another object of my invention is to provide a method for producing agrease having gelgrease properties but containing at-least some highviscosity oil.

Qther objects and advantages of my invention will become apparent uponreading the following specification.

I have found that a grease comprising a mixture of these two types ofgrease produced in a manner to be described retains the desirableproperties of each' type of grease and minimizes the undesirableproperties found in each type of grease. Initial step of the process isproduction of the two individual greases.

Soda base gel greases madewith oil of viscosity preferably of 150 to 500S. U. S. at 100 Rare heated toincorporate the sodium salt of a fattyacid into the oil. The mixture is cooled quickly and the resultingmassworkedto obtain a homogeneous mass of good penetration for a gel grease.Aluminum base gel greases are prepared by heating the aluminum salt ofthe fatty acid with ,the oil and the mixture is cooled slowly. Aftercooling this latter grease may or may not be worked to improve itshomogeneity. Lithium and other alkali metal gel greases are made inabout the same manneras the sodium greaseand they are likewise worked toobtain homogeneous greases of good stability.

The fiber grease is produced by saponification of a fatty acid, or anester, such as tallow. or

animal fat, in a high viscosity (e. g. greater than 150 S. U. S. andpreferably greater than 500 S. U. S. at 100 F.) lowV. I. (e. g. lessthan 90) oil to produce a mixture containing about 50 per cent soap. Thesoap concentrateisthen heated to 200-250 F. to remove most of the water.More cold oil of high viscosity and low V. I. is added with stirring toproduce the fiber grease. gel grease is then incorporated with stirring(not severe. working) into the fiber grease, the temperature in thismixing step being from 60 to 170 F., preferably from 110 to 140 F. It ispreferred that the two greases to be mixed should have about the sameconsistency. The final grease should comprise 5 to 95 per cent,preferably 20 to 70 percent, of the gel grease; and it shall containbetween 8 and 20 weight per cent soap.

The fibrous-gel grease, as the grease of this invention may be quiteaptly termed, has a fiber greases tendency to cling to metal surfaces,and has much less tendency to bleed than conventional gel grease. Thepresent greaseis also less temperature sensitive, whereas a conventionalfiber grease softens and a conventional gel The grease hardens onheating. It is especially noteworthy that the fibrous-gel grease is, asprepared by the process of this invention, quite work stable, and thusretains its lubricating properties during use.

In one specific embodiment of this invention, a neutral oil is solventextracted, for example with phenol, to produce a high V. I., parafiinicfraction and a low V. I., relatively non-paraifinic fraction. The highV. I. fraction is of relatively low' viscosity and the low V. I.fraction is of relatively high viscosity. The parafilnic fraction isthen used in making one grease constituent and the non-parafiinicfraction in making another. The two greases are thenmixed to produce thefibrous-gel grease of this invention.

The examples following all contain the same ingredients except Example 5which includes only the 170-180 S. U. S. oil of Example 1.

Example 1 A first gel-type grease was made from a-l- 180 S. U. S. oil(solvent extracted. Midcontinent neutral, V. I. above with 20 per centsodium stearate and worked .1000 strokes on an AN-G plate using an A. S.T. M. grease worker. A second or fiber-type grease was made from a. 750S. U. S. naphthenic oil (V. I. of 60) using 20 per centsodium stearate.The first grease was incorporated at F. with stirring into an equalportion of the second grease. The resulting grease was then worked80,000 strokes on the AN-G worker and had a micro-penetration after thistreatment of 114. The final product possessed desirable propertiesnormally attributed to gel grease and'to fiber greases.

Example 2 This grease was the same as the grease of Example 1 exceptthatthe oil not retained in the first grease prior to working wasdrained off and incorporated into the second grease during itsformation. The final grease produced was worked with the AN-G workerfor80,000 strokes, after which it hada micro-penetration of 148. The firstgrease of thisexample accordingly contained a little more-than 20 percent sodium stearate and the second grease constituent contained alittle less than 20 per cent sodium stearate. The greases of Examples 1and 2 are excellent fibrous gel greases.

Example 3 Same as Example 1, except that the first grease was not workedprior to incorporation into the second grease. After 80,000 strokes onthe AN-G grease worker, the micro-penetration was.303..

Example 4 A gel-type grease was made by mixing equal portions of the twooils of Example 1, adding sodium stearate to obtain a 20 per centconcentration in the final grease, heating to, 464 F., and quicklycooling. This grease after 80,000 strokeson the grease worker had amicro-penetration of 298.

Example 5 A gel grease of 20 per cent sodium stearate is made with the170480 viscosity oil of Example 1, and the grease is worked. This gelgrease has a micro-penetration of 70-75 after 80,000 strokes on the AN-Ggrease worker.

Example 6 A- lithium stearate gel grease was made-using 20 per centlithium stearate in -180 S, U. S.

oil of Example 1. A sodium stearate fiber grease was made using per centsodium stearate in 750 S. U. S. oil of Example 1. The two greases weremixed in equal proportions and worked 80,000 strokes using the AN-Gplate of the grease worker. The micro-penetration was 230. While notquite the equal of the greases of Examples 1 and 2 in work stability,this grease had good characteristics. Lithium base gel greasesordinarily have a penetration in the range of 200 to 250.

Example 7 An aluminum stearate gel grease was made using 20 per centaluminum stearate in 170-180 S. U. S. oil of Example 1. A sodiumstearate fiber grease was made using 20 per cent sodium stearate in 750S. U. S. oil of Example 1. The two greases were mixed in equalproportions and worked 80,000 strokes using the AN-G plate of the greaseworker. The micro-penetration was 126.

It will be noted that the fibrous-gel grease of Example 1 had nearly asgOOd work stability as the best gel grease, the grease of Example 5. Thefibrous-gel grease, however, has the additional advantage of clinging tometal surfaces and ease of retention in the bearing. A fiber-type greasealone will usually break down on 1000 strokes of working to a point ofbeing rather fiuid. Thus, the advantages of the present invention areevident from the previous examples.

It should be noted that my fibrous grease of Example 1 has a penetrationof 114 which value is substantially the equivalent of a good quality gelgrease. A grease of this latter type, as in Example 5, has a penetrationof 70-80. Greases which vary only points in penetration are consideredto have very nearly the same hardness or consistency. My fibrous-gelgrease of Example 1 exhibited the excellent penetration value of 114after 80,000 strokes in a grease worker. This might be contrasted with aconventional fibrous type grease which ordinarily breaks down to athick, soupy mass after 1000 strokes of working.

In the art this type of grease is believed to be a completely newgrease, one having workability properties of a good gel grease and yetthe clinging to metal surfaces and bleed-free properties of a fibergrease. Fiber greases withstanding 80,000 strokes on a grease worker andyet having a good penetration value is believed unknown in the art, as1000 strokes often breaks them down.

Comparing Example 1 with Example 5, it is unexpected that a mixture, nomatter how oompounded, of 50 per cent fiber grease, which breaks down in1,000 strokes, should be more than the average of such a fiber greaseand the gel grease of Example 5, yet unexpectedly the combined grease ofExample 1 was substantially as good under 80,000 strokes working as thatof Example 5, and had a non-bleeding, tacky character absent in thegrease of Example 5.

The above-described examples are given for illustrative purposes andshould not be regarded as limiting the invention, the scope of which isset forth in the following claims.

Having described my invention, I claim:

1. A method for producing a grease comprising mixing a fat with aquantity of oil, saponifying the fat of said mixture With a causticalkali in the presence of said oil, heating the saponified mixture to atemperature from 200 to 250 F.,

admixing with said saponified mixture an additional quantity of oil,stirring the admixture to produce a fiber structure therein, to thestirred fibrous admixture incorporating with stirring a quantity of gelgrease at a temperature between the limits of 60 to 170 F. and thequantity of gel grease incorporated comprises 5 to per cent of the finalgrease.

2. In the method of claim 1, incorporating said gel grease into saidstirred fibrous admixture at a temperature between the limits of to F.and the quantity of gel grease incorporated comprises 20 to 70 per centof the final grease.

3. In the method of claim 1, the proportion of fat mixed with saidquantity of oil is such as to yield a saponified mixture containing atleast 50 per cent soap.

4. A method for producing an improved grease comprising melting aneutral soap, admixing with the melted soap a quantity of a first oil toproduce a single oil-soap phase, cooling the mixture quickly and workingthe cooled mixture to produce a smooth first grease, adding to somefatty acid material a quantity of a second oil, saponifying said fattyacid material in the presence of said second oil with a caustic alkali,heating this saponified mass to a temperature between the limits of 200and 250 F., into the heated mass admixing an additional quantity of saidsecond oil, and into this latter admixture incorporating with stirringsaid first grease at a temperature between the limits of 60 to 170 E,the proportion of said first grease so incorporated constituting from 5to 95 per cent of the final grease product.

5. In the method of claim 4, said first oil has a viscosity index above90 and a viscosity between the limits of 100 and 700 seconds, SayboltUniversal at 100 F. and the second oil has a viscosity index below 90and a viscosity above 100 seconds, Saybolt Universal at 100 F.

6. In the method of claim 4, said first oil has a viscosity index above90 and a viscosity between the limits of and 500 seconds, SayboltUniversal at 100 F. and the second oil has a viscosity index below 90and a viscosity above 150 seconds, Saybolt Universal at 100 F.

7. In the method of claim 4, solvent extracting a lubricating oil stockto produce a raffinate oil having a viscosity index above 90 and aviscosity between the limits of 150 and 500 seconds Saybolt Universal assaid first oil, and an extract oil having a viscosity index below 90 anda viscosity above 150 seconds Saybolt Universal at 100 F. as said secondoil.

8. In the method of claim 4, the proportion of fatty acid material andsecond oil is so chosen that the saponification product thereof containsat least 50 per cent soap.

GEORGE F. FORD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,257,945 Fraser Oct. 7, 19412,475,589 Bondi July 12, 1949 OTHER REFERENCES Klemgard-LubricatingGreasespages 84, 85, 584 and 585, pub. 1937 by Reinhold Pub. Corp., NewYork, N. Y,

1. A METHOD FOR PRODUCING A GREASE COMPRISING MIXING A FAT WITH AQUANTITY OF OIL, SAPONIFYING THE FAT OF SAID MIXTURE WITH A CAUSTICALKALI IN THE PRESENCE OF SAID OIL, HEATING THE SAPONIFIED MIXTURE TO ATEMPERATURE FROM 200* TO 250* F., ADMIXING WITH SAID SAPONIFIED MIXTUREAND ADDITIONAL QUANTITY OF OIL, STRIPPING THE ADMIXTURE TO PRODUCE AFIBER STRUCTURE THEREIN, TO THE STIRRED FIBROUS ADMIXTURE INCORPORATINGWITH STIRRING A QUANTITY OF GEL GREASE AT A TEMPERATURE BETWEEN THELIMITS OF 60* TO 170* F. AND THE QUANTITY OF GEL GREASE INCORPORATEDCOMPRISES 5 TO 95 PER CENT OF THE FINAL GREASE.